Air film lubrication of marine vessels



Jan. 3L 1939. j- G SP|NANGER 2,145,463

AIR FILM LUBRICATION OI MARINE VESSELS Filed Sept. 8, 1956 In renfor- Patented Jan. 31, 1939 UNITED STATES PATENT OFFICE AIR FILM LUBRICATION-OF MARINE VESSEL 1 Claim.

My invention relates to a method for reducing the skin resistance of vessels and/or other bodies travelling in a liquid medium by the application of a thin lubricating air i'llm, thus reducing the power necessary for motion and making possible higher speeds with no additional expenditure of energy.

It is well known that in the construction of a vessel of a given displacement the resistance to motion, or skin resistance, is a function of the total underwater area of the vessel. This area is necessarily xed for a given displacement as any decrease in the area would correspondingly decrease the displacement. Aside from small variations due to form, and wind resistance in the superstructures, the skin resistance is the main obstacle to high speeds.

The salient object oi this invention is therefore to provide a means for reducing the skin resist'- ance by the application of a lm of air between the hull and the surrounding water.

Other objects of my invention are to make possible higher speeds at no additional increase in propelling power, tol make ship operation more economical through Asmaller power plants and larger cargo space.

Further objects and advantages of the invention will be apparent during the course of the following description.

In the accompanying drawing, forming part of this specification, and in which like numerals are employed to designate like parts throughout the same,

Figure lis a plan view of a vessel seen from the bottom up,

Figure 2 is a side elevation of the same vessel,

Figure 3 is a section along line 3-3 in Fig. 2,

Figure 4 is a section along line 4 4 in Fig. 1, and,

Figure 5 is a partial bottom view of Fig. 4.

Figure 6 is a cross section of a rudder or similar streamlined body.

In the drawing illustrating a preferred embodiment of my invention, numeral I0 designates the hull of a vessel while the dotted lines atI I, I2, I3, I4, I5 and I6 designate air-channels on the inside of the hull IIJ. The channel I3, for instance, is again divided into several sections through the dividing walls I'I, I8, I9 and 20 according to the hydrostatic pressure on the outside. In Figure 4 is shown a typical section of channel I4. These channels extend across the bottom of the vessel and up on the side almost to the waterline. The channels II and I2 extend from the bow downward and sideward on both sides. In Figure 4 the channel I4 is constructed from a steel member 2l which is welded at 22 and 23 to the hull plates 24 and 25. The seam between the plates 24 and 25 is riveted with rivets 26 but it is not calked and made tight in the usual manner. A small space is left open between the two plates 24 and 25 to let the air out. If necessary this space is regulated by placing thin washers 2l between the plates 24 and 25 leaving air channels as indicated with dotted lines and arrows in Fig. 5. The air bubbles 28 are leaving the channels in a rearward direction as shown in Figure 4.

In Figure 6 is shown hcw a rudder 29, or other body moving throughl water, may be lubricated with an air lm from a central pipe 30 through apertures 3I and 32.

In cases where the draft of the vessel makes a great difference between the hydrostatic pressure at the water line and at the bottom of the vessel the transverse air channels are divided as shown in Figure 3. The diierent sections are then supplied with air either from separate compressors at appropriate pressures or from a single van-type turbo-blower which may be bled at the proper pressure steps. The air is conducted from the compressor to the air channels through pipe connections 33 and 34 at the lowest pressure, the next pressure step is connected to pipes 35 and 36 and the last one to 31, all as shown in Fig. 3. It is obvious that many more steps may be used if desired, Aand the number of channels will be governed by the length and speed of the vessel. Similarly the air gaps or apertures through which the air leaves the hull may be graded according to the outside hydrostatic pressure so that equal amounts of air will flow at all points. The volume of the air flow will be governed by the pressure and may in each case be regulated until the vessel attains maximum speed.

The operation of my invention is simple and obvious from the description supra. By forcing air bubbles between the hull and the surrounding water the skin area is reduced, and the resistance or friction is reduced from friction in water to friction in air. Experiments have shown that the air is the best medium for this purpose and that it will tend to adhere to the solid body. The air bubbles thus elongate and flatten out and form an effective air cushion along the bottom and sides of the vessel. The vessel will thus be riding on air and the friction will be tremendously reduced. Due to the motion of the vessel the air bubbles will of course move with the water, but due to the greater adherence of the air to the hull the necessary amount of air will not be excessive.

Similarly in rough sea the air bubbles will receive a transverse motion, rst to one side and then to another, the effect of the two motions will cancel each other and will thus not impede the operation of the invention. To minimize the loss of air due to sideways rolling, the hull may be built with longitudinal corrugations similar to the belly of a whale. The eiect of the lubricating air film will be to greatly increase the speed of the vessel with a given power plant. If no higher speed isl desired the normal speed may be maintained with a much smaller power plant, thus saving in fuel cost and cargo space.

It is obvious from the description supra that the present invention may also be applied to the reduction of friction of other bodies moving through a liquid such as for instance hydroplane oats, rudders, hydraulic turbine rotors, Apropeller agitators, etc.

It will be seen that there has been provided a unique method and means for making the motion of vessels and bodies in a liquid more eiiicient. Although to present a complete disclosure of the invention there has hereinabove been described various details, shapings, materials, etc., it is obvious that these could be varied greatly without departing from the scope of the invention as defined by the appended claim.

I claim as new:

A system of supplying air lm lubrication to the underwater surface of vessels comprising an open plate seam traversing the bottom of the vessel in ,a transverse direction, the outside plate in said seam being forward of the inside plate; a spacer of suitable thickness placed over each rivet and between the two plates in said seam; an airtight channel covering said open seam on the inside of `the vessel and means for supplying air to said `channel under pressure capable of overcoming the static pressure.

JACOB G. SPINANGER. 

